A340509 a(n) = 3*A005382(n)-1.

5, 8, 20, 56, 92, 110, 236, 290, 416, 470, 596, 632, 686, 812, 920, 992, 1010, 1100, 1136, 1316, 1496, 1640, 1730, 1802, 1820, 1856, 1982, 2072, 2180, 2432, 2486, 2630, 2810, 2900, 2990, 3026, 3206, 3512, 3710, 3836, 3890, 4196, 4286, 4376, 4592, 4826, 4880, 4970, 5276, 5600

Offset: 1

Author

N. J. A. Sloane, Jan 27 2021, following a suggestion from Des MacHale

Keywords

• nonn

Comments

These are the numbers b(n) + 2*b(n)-1, where b is A005382, and so form a potentially infinite sequence of numbers which are the sum of two primes. An analog of A175666.

Crossrefs

Cf. A005382, A005383, A005384, A175666.

Programs

Maple

q:= p-> isprime(2*p-1):
map(x-> 3*x-1, select(q, [ithprime(i)$i=1..300]))[]; # Alois P. Heinz, Jan 27 2021

Mathematica

Select[Range[5600], And @@ PrimeQ[{# + 1, 2*# - 1}/3] &] (* Amiram Eldar, Jan 27 2021 *)

Formula

a(n) = A005383(n) + A005382(n). - Wesley Ivan Hurt, Feb 22 2022